1. Field of the Invention
The present invention relates to a measuring apparatus with an AE (Acoustic Emission) sensor; and, particularly, to a measuring apparatus with AE sensors, which detects the same AE signals with respect to the same events that damage a geotechnical structure, regardless of conditions and shapes of the ground in the geotechnical structure, thereby collecting reliable AE signals.
Further, the present invention relates to an installing method of the measuring apparatus with the AE sensor, and a set of the measuring apparatus with the AE sensor.
2. Description of Related Art
The present invention relates to a technology relevant to the field of rock mechanics and geotechnical engineering, particularly, a measurement technology for grasping failure signs of a geotechnical structure using Acoustic Emission (AE) signals generated by a damage of the geotechnical structure and also providing management standard for failure prediction. In detail, the present invention relates to a method of predicting failure of a geotechnical structure using the AE method instead of a conventional displacement or stress measuring method. Herein, the AE signal is an idea including AE and microseismic (MS) events.
AE is an elastic wave generated when energy of sudden strain relevant to damage of a material is emitted. Generally, generation of the AE signal is sharply increased before large-scale failure. As general technologies and equipments for predicting failure of a geotechnical structure, today, there is (are) a displacement measuring method using a rod extensometer, an inclinometer probe or GPS; a method of measuring a change in underground water level using a piezometer; and a stress measuring method using a load-meter. Since the strain before failure of a geotechnical structure is very small, it is difficult to grasp the failure signs using the conventional displacement or stress measuring method. However, before the failure of the geotechnical structure, microcracks are generated along with minute strain and then the microcracks are grown and coalesced with each other, whereby the failure occurs finally. Therefore, if it is possible to detect the microcracks, it is possible to grasp the signs of failure. In other words, before the final failure, the microcracks are generated in the geotechnical structure, and the microcracks cannot be detected by the displacement or stress but can be detected by the AE signals.
In a conventional measuring apparatus using the AE signals, a borehole was formed in the geotechnical structure, and a plurality of AE sensors is located at predetermined positions of the borehole along with a grouting material so as to measure the AE signals. The conventional measuring apparatus used as the grouting material a material having dynamic properties similar to those in a material of the geotechnical structure. However, since the geotechnical structure was comprised of various rocks and soils, it was difficult to use the same material as the material of the geotechnical structure. Further, there was another problem that the plurality of AE sensors were needed due to attenuation characteristics of the AE signals.
In other words, the geotechnical structure is comprised of various rocks and soils, which respectively have different dynamic and technologic characteristics according to their kinds and conditions. Therefore, even though the same damages are applied to the geotechnical structure, the AE signals generated by the damages are different according to the geotechnical structures. Thus, the AE sensor for sensing the AE signals senses the different AE signals with respect to the same events that damage the geotechnical structure, and it is difficult to consistently predict the failure of the geotechnical structure.